The long-term objectives of this research are to further our understanding of dynamic pattern formation in nonuniform reacting systems, particularly with respect to the role played by various modes of transport, and to apply the results to specific problems of spatial pattern formation in developmental biology. The specific objectives in this phase are motivated by three questions: (1) What are the minimal properties of the kinetic mechanism needed to produce stable pattern in an initially uniform system when transport occurs only by diffusion? by active transport? or, by a combination of these? (2) What conditions on the kinetics and the transport mechanism ensure pattern regulation? That is, when are the solutions of the governing equations invariant under certain changes of length and/or time scale and when can part of the pattern reproduce the whole? (3) What is the effect of pre-existing pattern on pattern formation and how might the succession from one pattern to another be controlled? The objectives are to: (1) classify three-component kinetic mechanisms according to the kinds of kinetic interactions needed for the existence of either stationary or oscillatory instabilities in the presence of diffusion alone, or both active transport and diffusion; (2) analyze general reaction-transport models to determine what properties the kinetics and transport mechanism must have, in order that stable steady states have pre-specified invariance properties under various changes of length, and concentration scales; (3) study simple examples of pre-existing pattern, such as that due to a gradient in some state variable, with the aim of understanding how stable complex patterns can arise from the successive build-up of simpler patterns.